Extracorporeal Membrane Oxygenation and EMS

Simon Taxel, NRP, BA, writes about the benefits of extracorporeal membrane oxygenation and discusses Pittsburgh EMS’s ECMO program.

A Case-Based Discussion of an EMS-Driven Out-of-Hospital Cardiac Arrest Referral Program

Case Study Part 1

My partner and I arrived on scene to find a 46-year-old male supine on the gymnasium floor. Bystanders were performing CPR, an AED was applied, and 1-shock had been delivered. The bystanders stated that the patient was playing basketball with friends when he suddenly complained of chest pain, sat down, and then became unresponsive. The bystanders immediately realized that the patient was suffering from cardiac arrest, began CPR, retrieved an AED, and called 911. We arrived on scene approximately seven minutes after the initial 911 call was made. There was no associated trauma and the bystanders denied seizure activity. I verified that the patient was pulseless and apneic while my partner attached the cardiac monitor.

The patient was found to be in ventricular fibrillation (VF) and a 200J biphasic shock was delivered. CPR was continued immediately after the patient was defibrillated. I established vascular access with an 18g angio catheter placed in the patient’s left antecubital vein and administered 1mg of 1:10,000 epinephrine IV and 300mg of Amiodarone IV while my partner placed an oral pharyngeal airway (OPA) and provided positive pressure ventilation. After two minutes of CPR, the patient’s cardiac rhythm was analyzed and was found to be refractory VF. Another 200J shock was delivered and CPR was continued.

Introduction

The standard ACLS resuscitation paradigm, which is validated by robust evidence, indicates that the majority of out-of-hospital cardiac arrest (OHCA) patients have the best chance of neurologically intact survival when aggressive resuscitation is performed on scene prior to patient movement and transport to the hospital.1 As such, one would think that the patient described in the case would be best served by extended on-scene resuscitation. However, this may not actually be true. In certain circumstances, there is a small cohort of OHCA patients who will have a much better chance of meaningful survival with a radically different approach to resuscitation, treatment and transport.2 These patients are likely experiencing such a significant cardiorespiratory event that sustainable return of spontaneous circulation (ROSC) will never be achieved unless the problem is corrected.

Enter extracorporeal membrane oxygenation (ECMO). ECMO is a procedure where a device similar to a dialysis machine takes over the role of the heart and lungs. A large catheter is placed in the patient’s femoral artery and another is placed in the femoral vein. Their blood is pumped through a machine with a membrane oxygenator that allows for the off gassing of carbon dioxide and the reoxygenation of hemoglobin. After that, the blood is rewarmed and then recirculated back into the body.3 ECMO effectively bypasses the heart and lungs and provides the time that is necessary for the cause of the cardiac arrest to be identified and corrected. In one study published in 2020, patients who were in refractory VF and received treatment that included rapid transport to the hospital and placement on ECMO had a survival rate of 43% as compared to patients that were treated along standard ACLS guidelines who had a survival rate of 7%.4

Related

The study was a Phase 2, single center, open-label, adaptive, safety and efficacy randomized clinical trial, that included adults aged 18-75 presenting to the University of Minnesota Medical center with OHCA and refractory VF, no ROSC after 3-shocks, mechanical CPR in the field, and an estimated down time of 30 minutes or less. Patients were randomly assigned to the ECMO trial or standard ACLS-based treatment. The results were so profound that the study was ended early so that all eligible patients could be enrolled in the ECMO program.5

In order to better understand the value of integrating ECMO into the treatment architecture of OHCA we must first have substantive knowledge of refractory VF. VF is a pernicious heart rhythm that is characterized by disorganized or fibrillating electrical currents moving through the conduction system of the heart’s ventricles. VF does not produce any meaningful perfusion and without early intervention with defibrillation and CPR, patients suffering from VF will quickly die. There are a multitude of causes of VF that are frequently described as the H’s and T’s. The H’s include hypoxia, hypovolemia, hypothermia, hyper/hypokalemia and hydrogen ions (acidosis). The T’s are tension pneumothorax, cardiac tamponade, toxins and thrombosis. Many of these causes of VF are meaningfully addressed with standard ACLS resuscitation which is reflected by the increased survival of OHCA when the patient’s initial rhythm is VF.

Refractory VF is ventricular fibrillation that is shock resistant and will not convert with standard defibrillation, due to ongoing myocardial ischemia that may be irreversible using standard ACLS treatment paradigms. Any VF that will not convert to a different rhythm “after at least three defibrillation attempts, 300 mg of amiodarone, and does not exhibit return of spontaneous circulation (ROSC) after greater than 10 min of CPR” is refractory.6 Refractory VF is frequently associated with severe structural heart disease.7 These insults are so significant that there is no viable collateral circulation, and no defibrillation, CPR, or medication will lead to ROSC. Among these patients ECMO provides better end organ perfusion and greater neuroprotection than standard CPR and provides a time bridge which allows the problem to be corrected while the patient technically remains in cardiac arrest.8

Case Study Part 2

The patient was in refractory VF after 3 shocks, continuous CPR, 2mg epinephrine IV, and 300 mg amiodarone IV. Based on the totality of the circumstances, I recognized this patient as a potential candidate for the ECMO referral program. I consulted with online medical command while my partner applied a LUCAS device and prepared the patient for transport. The command physician agreed that the patient would be more likely to benefit from rapid transport to an ECMO-capable facility rather than extended resuscitation on scene. We agreed to bypass the closest community hospital that was five minutes away and transport the patient to a tertiary care facility that was previously established as a partner in the ECMO referral program, which was 10 minutes away.

While we finished packaging the patient and prepared for transport, command notified the receiving facility. Their ECMO team was activated to meet us in the ED upon our arrival at the hospital. While we were en route to the hospital mechanical CPR was continuous, two more shocks were delivered, two additional 1 mg doses of epinephrine were administered, the patient was successfully intubated, and the endotracheal tube placement was verified and monitored using continuous wave form ETCO2 monitoring. The patient remained in persistent refractory VF.

Criteria for Prehospital ECMO Referral

ECMO is resource intensive, expensive, and is not readily available at all hospitals. It requires highly trained perfusionists whose sole responsibilities are the ECMO machines integrated with specialized teams of nurses, physicians and other allied healthcare providers. The paucity of ECMO throughout the healthcare system means that the first step in a successful prehospital ECMO referral program is for EMS providers to be able to promptly and accurately identify patients that will potentially benefit from the therapy. While the specific standards for ECMO referral vary somewhat from program to program the basic framework is consistent. OHCA patients that benefit from ECMO are those patients who experience witnessed cardiac arrest, are provided with bystander CPR prior to EMS arrival, present to ems with an initial shockable rhythm or PEA with organized complexes appearing at a rate greater than 20 per minute, and who appear to have had good neurocognitive functional status prior to the arrest event.

The specific criteria for Pittsburgh EMS ECMO referral are outlined in the checklist pictured in Figure 1. To be included in the Pittsburgh EMS program, the patient must be between age 18 and age 60, have good functional status prior to arrest which includes: living independently, no long-term care or nursing home residents, no prior neurocognitive dysfunction, and no evidence of end-stage disease. Patients that are morbidly obese or are otherwise so large (or too small) that a LUCAS device is unusable are excluded because manual CPR during transport is ineffective. The patient’s ETCO2 must be greater than 10mm/Hg with CPR and EMS must have the ability to deliver the patient to an ECMO-capable emergency department (ED) within 30 minutes of their initial collapse. The checklist is available to all crews, but its primary use is at the command center where the faculty physician on duty will review the checklist with the crews on scene and then if all criteria are met will activate the ECMO team at the receiving facility. Currently, personnel are not permitted to request ECMO activation without consulting the faculty physician.

Figure 1

The Treatment Paradigm for ECMO Referral

The prehospital treatment paradigm for successful ECMO referral is dependent on early recognition, significantly attenuated on scene time and rapid transport to the appropriate receiving facility. On scene EMS personnel must recognize potentially eligible patients early, run the checklist with command, apply the LUCAS device, and have the patient packaged and prepared for transport as quickly as possible. The goal is to have the patient packaged, extricated, and ready for transport within 20 minutes or less after EMS arrives on scene. There is a myriad of potential barriers to the implementation of this program that include response time, extrication and patient movement problems that take significant time to work, as well as transport time to the receiving facility. Additionally, it can also be challenging for paramedics that have spent countless hours refining their tactics for aggressive on-scene resuscitation of OHCA to rapidly change gears and approach the situation with a strategy that is diametrically opposed to standard practice.

Case Study Part 3

Upon arrival at the hospital, the ECMO team was ready and waiting for the crew in the ED. The patient was canulated and placed on ECMO immediately. After a coronary angiography was completed and a 100% occlusion of the left main coronary artery was identified and stented. Once the stent was placed, the patient’s heart was successfully re-perfused and the patient’s heart rhythm quickly converted to a normal sinus rhythm. A few days later the patient stabilized, was extubated, and was found to be neurologically intact. He did not remember anything after he arrived at the gymnasium and started to play basketball. Five days after the patient experienced cardiac arrest, he was discharged home in good condition, without any neurocognitive deficits.

The Challenges and Lessons Learned

There are a variety of challenges that must be anticipated and prepared for in order for an organization to implement an effective ECMO referral program. The first is that the cohort of eligible patients is incredibly small and eligible OHCA’s that meet criteria occur infrequently at best. The Pittsburgh Bureau of EMS is a large urban EMS system that responds to excess of 70,000 emergencies annually and there are zero-to-one ECMO eligible cases each month. It is abundantly clear that paramedics and EMTs are excellent at skills and interventions that they perform regularly. Unfortunately, the skills and knowledge of our profession are perishable so the scarcity of eligible ECMO patients and their treatment plan which is so different than standard practice presents a significant barrier to implementation. To be successful, organizations must counter act this with frequent training to encourage personnel to recognize eligible patients as expediently as possible.

Another factor that can be severely limiting is the initiation of bystander CPR prior to ems arrival. In the Pittsburgh EMS program, the cardiac arrest must be witnessed and bystander CPR must be provided in order to enroll the patient in the program. It is imperative that EMS organizations partner with community stakeholders to promote lay rescuer CPR training. It will help to increase the number of ECMO eligible patients and it will undoubtedly save lives. Standard CPR has been shown to be ineffective when performed in a moving ambulance.9 Consequently, access to mechanical CPR is required for eligibility. The Pittsburgh Bureau of EMS only has three LUCAS devices deployed throughout the entire system. They are placed on rescue units that are typically dispatched to every cardiac arrest but if there is no Lucas available then the patient becomes ineligible. The current evidence suggests that absent a scarcity of personnel to perform CPR, there is no increase in neurologically intact survival when mechanical CPR is used.10

More from the Author

Mechanical CPR is not recommended for routine use by the American Heart Association (AHA) and it is considered class 2b which means that its usefulness/effectiveness is unknown.11 It is for these reasons that mechanical CPR devices are not more widely utilized in the Pittsburgh EMS system but for patients to be referred to ECMO it must be available. ECMO for OHCA patients is only performed at select hospitals. In Pittsburgh, there is currently only one hospital that will perform it. There is a second facility that hopes to have an ECMO program online within the next few months, but it is not yet operational. This creates geographical challenges that can become insurmountable. If the scene of the call is remote from the one hospital that will perform ECMO than patients can be rendered ineligible simply by the amount of time it will take to transport them there.

A novel program has recently been implemented in Minnesota to increase the number of facilities that are capable of providing ECMO to OHCA patients.12 The Minnesota Mobile Resuscitation Consortium (MMRC) have deployed an ECMO team consisting of two specially trained physicians and a nurse or paramedic that are available to respond around the clock. When they are activated by the dispatch center, they respond and meet EMS crews at any one of three designated receiving facilities and initiate ECMO in the ED. In the future, they hope to be able to use this response capability to be the groundwork for field canulation and the initiation of ECMO before the patient even reaches the hospital. Finally, there is an ongoing debate among the experts as to whether the cannulation for ECMO should be performed in the ED or if the patient needs to be in the catheterization lab where it can be completed with fluoroscopy. This must be settled by hospital and prehospital partners before a patient is ever enrolled in the program.

A successful ECMO referral program requires strong partnerships between EMS agencies, receiving facilities and community stake holders. Frequent scenario-based training that involves not only the medical interventions, but the logistical challenges of prehospital care are an effective way to increase the knowledge and readiness for everyone involved. This means that scenarios will have to be run from the time a patient collapses, until EMS arrives, treats, packages, extricates and transports the patient to the receiving facility where the in-hospital team receives the patient and takes over care. If lay-rescuers within the community, EMS providers, and in-hospital personnel all train and prepare in separate silos this type of program is going to be hamstrung from the very beginning. Successful ECMO referral for OHCA truly requires strong integration of all individuals and agencies that are involved to foster a collaborative partnership that functions rapidly and efficiently during these high stress low frequency events.

Note: The case presented in this discussion is fictional and is intended to contextualize the information that is presented.

References

1. Grunau B, Kime N, Leroux B, et al. Association of Intra-arrest Transport vs Continued On-Scene Resuscitation With Survival to Hospital Discharge Among Patients With Out-of-Hospital Cardiac Arrest. JAMA. 2020;324(11):1058–1067. doi:10.1001/jama.2020.14185

2. Bartos, Jason A. Frascone, R.J. Yannopoulos, Demetris. Et Al. The Minnesota mobile extracorporeal cardiopulmonary resuscitation consortium for treatment of out-of-hospital refractory ventricular fibrillation: Program description, performance, and outcomes. EClinicalMedicine. 2020 Dec; 29-30: 100632. Published online 2020 Nov 13.

3. Extracorporeal membrane oxygenation (ECMO). Mayo Clinic Website. Available at: https://www.mayoclinic.org/tests-procedures/ecmo/about/pac-20484615. Accessed May 28, 2021.

4. Bartos, Jason A. Frascone, R.J. Yannopoulos, Demetris. Et Al. The Minnesota mobile extracorporeal cardiopulmonary resuscitation consortium for treatment of out-of-hospital refractory ventricular fibrillation: Program description, performance, and outcomes. EClinicalMedicine. 2020 Dec; 29-30: 100632. Published online 2020 Nov 13.

5. Yannopoulos D, et al. Advanced reperfusion strategies for patients with out-of-hospital cardiac arrest and refractory ventricular fibrillation (ARREST): a phase 2, single center, open-label, randomized controlled trial. Lancet, 2020 Dec 5; 396(10,265): P1807–P1816.

6. Nademanee K, Taylor R, Bailey WE, Rieders DE, Kosar EM. Treating electrical storm : sympathetic blockade versus advanced cardiac life support-guided therapy. Circulation. 2000;102:742-747.

7. Peppin, Jeff. Becoming the Ben Franklin of Ventricular Storm. Critical Care now. https://criticalcarenow.com/becoming-the-ben-franklin-of-ventricular-storm/. First Published February 23, 2021.

8. Yannopoulos D, et al. Advanced reperfusion strategies for patients with out-of-hospital cardiac arrest and refractory ventricular fibrillation (ARREST): a phase 2, single center, open-label, randomized controlled trial. Lancet, 2020 Dec 5; 396(10,265): P1807–P1816.

9. Russi, Christopher S. Myers, Lucas A. White, Rodger D. A Comparison of Chest Compression Quality Delivered During On-Scene and Ground Transport Cardiopulmonary Resuscitation. Western Journal of Emergency Medicine. 2016 Sep; 17(5): 634–639. Published online 2016 Jul 19. doi: 10.5811/westjem.2016.6.29949

10. Rubertsson S, Lindgren E, Smekal D, Ostlund O, Silfverstolpe J, Lichtveld RA, et al. Mechanical chest compressions and simultaneous defibrillation vs conventional cardiopulmonary resuscitation in out-of-hospital cardiac arrest: the LINC randomized trial. JAMA. 2014;311(1):53–61.

11. Mechanical CPR Devices: Where is the Science? JEMS Website. Available at https://www.jems.com/exclusives/mechanical-cpr-devices-where-is-the-science/. Accessed June 2, 2021.

12. Yannopoulos D, Bartos JA, Martin C, et al. Minnesota resuscitation consortium’s advanced perfusion and reperfusion cardiac life support strategy for out-of-hospital refractory ventricular fibrillation. J Am Heart Assoc, 2016; 5(6): e003732.

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